In vehicles of public transportation, route information for the vehicles, information from government offices, and advertisement from private enterprises conventionally have been provided or displayed through paper medium in a fixed manner to the users. Recently, a part of the information is digitized; through electronic message boards using LEDs or liquid crystal displays, information on destinations, stops, transfers, or the like is variably displayed according to traveling sections, and advertisement is provided or displayed in the form of moving images or still images.
Patent Document 1 describes a display method of combining image data that are graphic data with relatively high luminance and image data of a natural image with relatively low luminance to generate and display image data. This method adjusts the maximum luminance of the image data with high luminance according to a feature amount of the image data with low luminance, combines the adjusted image data with high luminance and the image data with low luminance to generate display image data, then determines the brightness of a backlight according to a feature amount of the display image data, and adjusts the display image data according to the brightness of the backlight.